There are currently three major types of dental restoratives and cements that can be categorized by their method of cure. The first are self-cured materials, where the materials usually comprise a two-part system in which the curing process is initiated by mixing the two parts of the system. The second are light-cured materials wherein a generally one part system cures as a result of irradiation by high intensity light. The third are saliva-cured materials, wherein the material cures as a result of the formation of adducts between inorganic components present in the formulations with the water of the saliva, or as a result of a reaction of two or more chemical components of the formulation initiated by water of the saliva.
While the first two types are primarily used for permanent dental restorations, the third type is usually limited to temporary restorations where the material is expected to reside in the mouth for a short period of time, typically on the order of seven days or less. Ideally, a material useful for temporary applications should feature easy and fast application, short curing time, low cost, long shelf-life, good depth of cure, biocompatibility, resistance to oral fluids, satisfactory mechanical strength, ease of removal, and compatibility with permanent restoratives and cements.
Early versions of saliva-cured type temporary restoratives and cements were less than ideal and frequently generally inadequate in many respects. The curing time was generally slow (usually over 3 hours in an oral environment) making the material vulnerable to premature deterioration, especially during the hours immediately after application. The curing of the material progressed very slowly, and the depth of cure was frequently limited to a layer within a few millimeters of the contact of the material with saliva. Additionally, poor resistance to mastication forces, wear, and oral fluids frequently resulted in excessive premature deterioration of the restorations or structural failures.